The present invention relates generally to a system for cutting through ice.
Geologists presently feel that off-shore regions in the Arctic show great promise for the exploration and production of oil and gas. This expectation is bolstered by major gas and oil finds recently made on land in the vicinity of the MacKenzie Delta and Prudhoe Bay, and by the fact that off-short areas are usually more productive than adjacent land areas. When off-shore drilling operations are conducted in a temperate zone, conventional shallow water drilling methods and production platforms may be employed. However, in view of the extreme cold and harsh conditions which exist north of the Arctic Circle, the drilling and maintenance of off-shore wells in the Arctic has been extremely difficult. Particularly since the Arctic Ocean is covered with an ice sheet for a good portion of the year. The ice sheet may typically be five to six feet in depth, and an eight to ten feet sheet is not uncommon. Further, the Arctic ice sheet is characterized by extreme irregularities resulting from deformations thereof. One form of ice sheet irregularity is called a pressure ridge, which is normally a long narrow section of ice which has been built up to be many times thicker than the thickness of the surrounding ice sheet. Pressure ridges sometimes extend fifteen feet or more above the surface of the ice sheet and fifty feet or more below the surface. The movement of the ice sheet depends upon its location in the Arctic. At some locations the ice sheet moves only slightly, while at others movements of up to one mile per day, at a rate of up to five miles per hour, are not uncommon. Under these condition, it is extremely important to protect structures in such an environment from damage due to ice movement. One protection approach has been to cut through the ice as it moves against the structure. In view of the above, it is an object of the present invention to achieve a more efficient ice cutting system.
U.S. Pat. No. Re 28,332 discloses an ice cutting apparatus in which power jets around the circumference of the ice cutter are utilized to power the cutting blades past the ice. However, aside from powering the cutter blades, this patent does not disclose or teach any of the advantages of injecting a low density fluid into the ice cutting region.